Twisted thread assemblies



Sheet Filed Aug. 9, 1967 1 May 13, 1969 Filed Aug. 9, 1967 G. W. WALLSTWISTED THREAD ASSEMBLIES United States Patent O 3,443,370 TWISTEDTHREAD ASSEMBLIES Gordon W. Walls, Geelong, Victoria, Australia,assignor to Commonwealth Scientific and Industrial ResearchOrganization, East Melbourne, Victoria, Australia Filed Aug. 9, 1967,Ser. No. 659,483 Claims priority, application Australia, Aug. 9, 1966,9,432/ 66 Int. Cl. D01h 7/86, 7/90 U.S. Cl. 57-34 12 Claims ABSTRACT OFTHE DISCLOSURE Process for forming twisted thread assembly in twostages. In the first stage a group of strands is caused to ply-twisttogether to form a first thread by the steps of individually twistingone or more of the strands to impart alternating twist thereto andconverging the strands. In the second stage the first thread and asecond thread are caused to ply-twist together by applying steps similarto those of the first stage to the threads.

CROSS REFERENCE TO RELATED APPLICATIONS 'Ilhe present invention is adevelopment from the invention disclosed in US. Patent No. 3,225,533 andmay be performed by means of apparatus developed from the apparatusdisclosed in co-pending US. patent application No. 498,433.

BACKGROUND OF INVENTION Field of invention This invention relates to theformation of twisted thread assemblies and is applicable particularly,but not exclusively, to the preparation of yarn comprised of staplefibers, for example wool fibers.

Prior art The complete specification of US. Patent No. 3,225,- 533discloses the preparation of a yarn by twisting a strand so that it hasrepeated along its length alternating zones of opposite twist andconverging that twisted strand with another strand and allowing it totwist around that other strand. Both of the strands, or all of them ifthere be more than two, may be intermittently twisted and converged withthe regions of twist in the strands suitably phased so that, when thestrands commence to untwist, they twist around each other and thisplying of the strands restrains the twist in each individual strand toresult in a self-stabilized plied assembly. Such an assembly willhereinafter for the sake of convenience be called self-twist thread or,where appropriate, more specifically self-twist yarn.

Co-pending US. patent application No. 498,433 discloses roller twistingapparatus for producing self-twist yarns.

A self-twist yarn can be produced at much faster rates than conventionalplied yarns. However, it has been found that simple self-twist yarns arenot entirely satisfactory in all weaving and knitting applications. Thepresent invention is a development of the invention disclosed in US.Patent No. 3,225,533 and, as will be explained in detail hereinafter, itenables the formation of a yarn particularly suitable for weaving oralternatively a yarn which can be knitted most successfully and bothtypes of yarn can be produced at the same rate as simple self-twistyarns.

3,443,370 Patented May 13, 1969 SUMMARY According to the invention thereis provided a process for forming a stable twisted thread assembly,comprising individually twisting at least one strand of a group ofstrands so that each twisted strand has repeated along its lengthsuccessive zones of opposite twist separated by strand twist change-overregions at which there is no twist, converging the strands of the groupso that they twist around one another such as to form a stable firstthread having successive zones ofopposite plying twist separated byplying twist change-over regions at which there is no plying twist,twisting said first thread to superimpose alternately opposite twist insuccessive zones along its length which latter zones are separated bysuperimposed twist change-over regions of no superimposed twist, andconverging the twisted first thread with a second thread so that the twothreads twist around one another to form a stable twisted assembly.

The second thread may be a single strand or alternatively it may beformed by individually twisting at least one strand of a further groupof strands so that each twisted strand of the further group has repeatedalong its length successive zones of opposite twist separated by strandtwist change-over regions at which there is no twist and then convergingthe strands of the further group so that they twist around one anothersuch as to form said second thread as a stable assembly havingalternating zones of plying twist separated by plying twist change-overregions at which there is no plying twist.

Before the second thread is converged with the first thread, it may betwisted such as to impart alternately opposite twist to successive zonesalong its length which latter zones are separated by change-over regionsof no imparted twist.

The invention also provides a yarn comprised of a stable twisted threadassembly formed by the above-defined process.

The invention further extends to the provision of apparatus forproducing a stable twisted thread assembly, comprising first twistingmeans simultaneously to impart successive zones of opposite strand twistto each strand of a group of strands, first converging means adjacentthe first twisting means to converge the strands of the group to form afirst thread, second twisting means to superimpose successive zones ofopposite twist upon the first thread and second converging meansadjacent the second twisting means to converge the first thread with asecond thread.

In order that the invention may be more fully explained, one form ofapparatus and its use in the production of warp yarns in weaving andalso knitting yarns will now be described in detail with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIGURE 1 is a somewhat diagrammaticperspective view of one form of apparatus constructed in accordance withthe invention;

FIGURE 2 is a front elevation of the apparatus illustrated in FIGURE 1;

FIGURE 3 is a diagrammatic plan view of the apparatus;

FIGURE 4 is a diagrammatic representation of a two-strand self-twistthread produced at an intermediate stage in the production of a yarn bymeans of the apparatus;

FIGURE 5 is a diagrammatic representation of one four-strand yarn whichcan be produced by the apparatus;

FIGURE 6 is a diagrammatic plan view of part of the apparatus and showshow the path of a thread passing through it can be altered so as tochange the twist distribution in the final yarn; and

FIGURE 7 is a diagrammatic plan view of part of the apparatus showinghow it can be operated to produce a three-strand yarn.

Description of preferred embodiments The illustrated apparatus comprisesa conventional drafting unit 11 and two pairs of oscillating twistingrollers 12, 13 of the type illustrated in FIGURES 1 to of co-pending US.patent application No. 498,433, now Patent No. 3,377,792. The roller ofeach pair 12, 13 are rubber covered and arranged so that they are justtouching or with a small gap between them. These rollers are driven sothat they reciprocate in opposite phase and rotate in oppositedirections so that their adjacent surfaces move in the direction inwhich strands are fed forwardly by the drafting mechanism atsubstantially the same speed. The two roller assemblies are identical,in each case the rollers being mounted on a pair of shafts 14, 15 whichare rotated at constant speed in opposite directions through a geardrive 10 from an input belt drive 14. In order to allow them to rotatewith the shafts and at the same time to be reciprocated, the rollers arekeyed to the shafts by feather keys which are free to slide in alongkeyways so as to allow relative sliding movement between the rollers andthe shafts, The rollers of each pair are engaged by a pair of yokes 17,18 in such a way that relative rotation between the roller and the yokecan occur but no relative translation is permitted. These yokes areconnected by means of belts, pins, chains or the like 19, 20 to wheels21, 22. The wheels 21 of the two oscillating roller assemblies areconnected to a common drive shaft 16 by means of a pair of cranks 23 andconnecting rods 24, shaft 16, which is rotated by a belt drive 25, issplit at a position between cranks 23 and the two shaft portions thusformed are releasably coupled by means of a dual-sprocket andduplex-chain coupling in order to allow the positions of the twoconnecting rods 24 to be adjusted relative to one another. The yokes ofthe two oscillating roller pair assemblies are thus caused toreciprocate on their guides 26, 27 and thereby to reciprocate therollers as they are simultaneously rotated by gear drives 10. Thecoupling of the two roller mechanisms together by shaft 16 causes theoscillatory movements of the two roller pairs to maintain a requiredphase relationship to each other. This phase relationship will beexplained hereinafter.

FIGURES 3 to 5 illustrate the manner in which the apparatus may beemployed to produce a four-strand yarn which is particularly suitablefor weaving. Four spaced strands 31 are passed from drafting unit 11through the first pair of twisting rollers 12. These rollers impart toeach thread 31 alternating zones of opposite twist, which zones are ofequal length and are separated by twist change-over regions at whichthere is no twist. On leaving rollers 12, the strands are immediatelyconverged in two pairs by means of a pair of convergence guides 32 toform two intermediate self-twist yarns 33 each consisting of two of thestrands 31 plied together with their twist zones in phase. Theconfiguration of a self twist yarn produced merely by converging a pairof strands having the twist distribution of strands 31 and with theirtwist zones in phase is illustrated in FIGURE 4. The mechanism of theself-twisting is fully described in the complete specification of US.Patent No. 3,225,533 and the yarn of FIGURE 4 is identical to the oneillustrated in FIGURE 11a of that specification. In present FIG- URE 4,the symbol 2 is used to indicate regions in the strands in which thereis no strand twist and the symbol A -is used to indicate regions in theyarn in which there is no plying twist, regions 2 and A beingsubstantially coincident. In the zones between these regions in whichthe strands have individual S-twist the yarn has plying Z- twist and inthe zones in which the strands have individual Z-twist the yarn hasplying S-twist. Intermediate yarns 33 would have the configurationillustrated in FIG- URE 4 but for the action of the second pair oftwisting rollers 13. However, these intermediate yarns pass throughrollers 13 which superimpose alternating zones of opposite twist uponthem. The action of rollers 13 alters the configuration of yarns 33immediately they are formed. However, the resultant configuration andtwist distribution of each of the two yarns leaving twisting rollers 13is that of a yarn as illustrated in FIGURE 4 which has alternating zonesof opposite twist superimposed on it.

The superimposed twist distribution imparted by rollers 13 is similar tothe twist distribution given to the strands 31 by the first set oftwisting rollers 12 but the two sets of rollers 12, 13 are so spacedfrom one another and their oscillating motions so phased with respect toone another that the changeover regions of superimregions 22, A.

On leaving the second pair of twisting rollers 13, the two yarns havingthe superimposed further twist are immediately converged by means of aconvergence guide 34 and self-twisted together to form a stablefour-strand yarn 35 which is wound onto a take-up package 36.

Because a self-twist yarn of the configuration illustrated in FIGURE 4is stable (i.e. has complete torque balance), the torgue distribution ofeach of the pair of yarns leaving twisting rollers 13 is that of astrand having the superimposed twist distribution imparted by rollers13. However, the superimposition of the further twist on the self-twistyarn 33 causes the actual plying twist in some parts of the yarn to bediminished and in other parts to be reinforced so that the regions A ofno plying twist are displaced. The zones 2 of no strand twist are notdisplaced appreciably by the twist imparted by rollers 13,

The oscillatory motion of rollers 13 is so phased with respect to thatof rollers 12 that the final yarn 35 has the configuration depicteddiagrammatically in FIGURE 5. In this figure, the individual strands ofonly one of the intermediate yarns 33 are indicated, the secondintermediate yarn being shown in outline only. The two individualstrands which are illustrated bear shading lines to indicate theirstrand twist distributions. The strand twist distributions of allfour-strands are identical. The regions of zero plying twist between theintermediate yarns 33 are indicated by the symbol 6 and these regionsare displaced from the regions A of zero plying twist within the twoyarns 33 which latter regions are also displaced from regions 2. of zerostrand twist.

The yarn structure illustrated in FIGURE 5 is particularly applicable towarp yarns for weaving. Warp yarns should have relatively high strengthand abrasion resistance to withstand the tension and rubbing to whichthey are subjected during weaving. Simple self-twist yarns have regionsof no plying twist which have low abrasion resistance and alsoconstitute zones of weakness in the yarn. The use of such yarns as warpyarns can therefore lead to yarn breakage problems during weaving.However, because of the displacement of the various regions of zerotwist in the structure of FIGURE 5 it is possible to produce a wool yarnof this structure which has adequate strength and abrasion resistancefor use as a warp yarn.

The free length through which the converged strands 31 travel betweenconvergence guides 32 and the second pair of twisting rollers 13 shouldbe such as to allow an ample distance over which the converged strandscan twist around one another as is more fully described in US. patentspecification 3,225,533. The free length should be at least the lengthof a strand twist zone. For a similar reason, the distance between theconvergence guide 34 and take-up package 36 should preferably be atleast the length of one zone of twist imparted by rollers 13.

The distance between the two pairs of twisting rollers, indicated as Xin FIGURE 1, should preferably be at least one twist cycle length. Forthe preparation of wool yarns the distance X is preferably in the range12 to 40 cm., an optimum value being between 25 to 40 cm., and thestroke of each pair of twisting rollers should be in the range 2 to 7inches.

It has been found that, when preparing wool warp yarns of the structureshown in FIGURE 5, optimum results are achieved if the strokes of bothpairs of rollers are approximately equal and approximately 3 to 4%inches. The oscillation frequencies of the two pairs of rollers shouldbe the same and are preferably chosen with respect to the speed ofrotation of the rollers to give cycle lengths in the range 12 to 40 cm.More particularly it is preferred that the cycle lengths be between 20and 25 cm.

The requirements of a knitting yarn are different from those of a warpyarn in weaving. Strength and abrasion resistance are the most importantcriteria for a warp yarn and since, in a woven structure the yarn isheld quite firmly by the interlacing threads, residual torque in theyarn is not critical, However, a knitted fabric is formed with the yarnat one tension and the tension is then allowed to relax. The new relaxedtension requires a different twist level for torque balance and, if asimple selftwist yarn having high residual twist is used, it tends totwist up back to its torque equilibrium condition which causesdeformation of the knitted stitches and consequent distortion of thefabric. A four-strand wool yarn produced in the manner described aboveto have the structure of FIGURE 5 will also suffer from this defect ifknitted. However, a satisfactory knitting yarn can be produced byreducing the intensity of twist imparted by the second pair of twistingrollers thereby to reduce the intensity of self-twisting between the twointermediate yarns and altering the path length of one of theintermediate yarns as shown in FIGURE 6 so that when the two areconverged the regions of no strand twist 2 and the regions of no plyingtwist A of one yarn are not coincident with the regions 2 and A of theother yarn.

As shown in FIGURE 6, the length of the path followed by one of theintermediate yarns (identified as 33A), as it passes from itsconvergence guide 32 to the second pair of twisting rollers can beincreased simply by providing two further guides 37, 38. The increasedpath length is such that when the yarn 33A is self-twisted with theother yarn 33B after leaving the second pair of twisting rollers, itsregions 2, A are displaced by approximately one half of a cycle lengthfrom the regions 2, A in yarn 33B. Furthermore the stroke of the secondpair of twisting rollers is reduced so that it is less than that of thefirst pair of twisting rollers. It has been found that satisfactory woolknitting yarn can be produced if the stroke'of the first pair of rollersis 2 inches and the stroke of the second pair of twisting rollers isabout 1 inch.

A further modification aimed at reducing the tex. (i.e. weight per unitlength) of the resultant yarn is illustrated in FIGURE 7. The yarnsproduced by the arrangements shown in FIGURES 3 and 6 each havefour-strands. The finest wool strand which can conveniently be spunwithout breaking problems depends on the fineness of the wool fibres.For wool having an average fibre diameter of about 24 microns the finestpracticable strand is about 15 tex. so that a four-strand yarn made fromsuch wool must be at least 60 tex. Finer yarns are required for weavingsome types of fabric. A finer, yet weaveable, three-strand yarn can beproduced by means of the arrangement shown in FIGURE 7 and employing acontinuous filament structure (either multi-filarnent or mono-filament)as at least one of the strands. In this arrangement only two strands 41are passed through the first set of twisting rollers 12 and thenconverged to form a self-twist intermediate yarn 43. A third strand 44in the form of'a synthetic mono-filament is fed through a guide 45directly to the second set of twisting rollers 13. The second set oftwisting rollers impacts alternating twist to mono-filament 44 and theintermediate two-strand yarn 43, and mono-filament 44 and yarn 43 arethen converged by a convergence guide 46 'whereupon they self-twisttogether to form a resultant three-strand twisted yarn 47. Strand 44 maybe any synthetic monofil, for example nylon, polyamide, polypropyl ene,alginate or other rayon, an acrylic or polyester monofil. Each ofstrands 41, 42 may be wool or a synthetic monofil. For example strand 41might be a 9 denier nylon monofil, strand 42 a 15 tex. wool strand, andstrand 44 a 9 denier nylon monofil. This will give a resultant yarn 47of 17 tex. which is readily weavable. Furthermore this yarn will be 88%-wool and it will have many of the physical properties of a pure woolyarn.

The use of mono-filaments is not, of course, limited to the arrangementof FIGURE 7. A three-strand structure could be achieved by passingstrand 44 directly to convergence guide 46 without twisting it andallowing yarn 43 to twist around it. When producing a four or morestrand structure with the arrangement of FIGURE 3, mono-filament may beused as any of the strands 31.

The twist levels and strength of the yarns according to the inventioncan be altered by treatment with various kinds of additives. Forexample, if the strandsused in the preparation of a wool yarn aretreated with colloidal silica, their inter-fibre friction is increasedand it has been found that this will alter the twist levels in theresultant yarn and will greatly increase its strength. It has been foundthat wool yarns produced in accordance with this invention areparticularly susceptible to such treatment. The effect of such atreatment is illustrated by Example 2 below.

The following examples show the application of the present invention tothe production of weaving and knitting yarns. The yarns were producedwith the arrangements shown in FIGURES 3, 6 and 7.

EXAMPLE 1 Material.-Noble combing wool of 23 microns average fibrediameter.

Method.-Twisting was accomplished with the arrangement shown in FIGURES1 to 3. Each roller unit had a 3 inch stroke and imparted alternatingtwist of 22 cms. cycle length. (As used herein the term cycle length"designates a length of yarn occupied by a complete cycle of S and Ztwist, i.e. 2 consecutive twist zones.)

The roller units were phased relative to one another so that in thefinal yarn the resultant yarn twist due to the second set of rollers hadchange-over points exactly midway between twist change-over points inthe individual strands. produced by the first set of rollers.

Yarn properties.The yarn count was 55 tex. and the tenacity was 5.5gm./tex. with a coeflicient of variation of strength of 9.8%. The meansextension to break was 13% The number of turns of piled twist in eachhalf cycle of pliel twist in each intermediate yarn was 42 and thenumber of turns of plied twist in each half cycle of plied "twist in thefinal yarn was 27.

This yarn was suitable for use as a wrap yarn in weavmg.

EXAMPLE 2 Material.As in Example 1.

Method.The yarn was prepared in the same manner as in Example 1 but with1% colloidal silica added to the wool.

Yarn properties.The yarn count was 55 tex. and the tenacity was 8.0gm./tex. with a coefiicient of variation of strength of 9.6%

The mean extension to break was 29%. v v

The number of turns of plied twist in each half cycle of plied twist ineach intermediate yarn was 39 and the number of turns of plied twist ineach half cycle of plied twist in the final yarn was 29.

This yarn was suitable for use as a wrap yarn in weaving.

7 EXAMPLE 3 Material.-Noble combing wool of 23 microns average fibrediameter. 1 tex. nylon filament.

Method.The twisting was accomplished with the arrangement shown inFIGURE 7, two all wool strands being twisted by the first pair oftwisting rollers and then converged to form an intermediate yarn. Thisintermediate yarn and the 1 tex. nylon filament were twisted by thesecond set of twisting rollers and converged to form the resultantthree-strand yarn.

The two roller units each had a stroke of 3 inches and a twist cyclelength of 22 cms. and were phased relative to each other so that in thefinal yarn the resultant yarn twist due to the second set of rollers hadchangeover points exactly midway between the twist change-over points inthe individual strands due to the first set of rollers.

Yarn properties.--The yarn count was 55 tex. and the tenacity was 4.8gm./tex. with a coefiicient of variation of strength of 16%. The meanextension to break was 14% and the yarn was 98% wool and 2% nylon.

The number of turns of plied twist in each half cycle of plied twist inthe intermediate yarn was 39 and the number of turns of plied twist ineach half cycle of twist in the final yarn due to the second pair ofrollers was 29.

This yarn was suitable for use as a wrap yarn in weaving.

EXAMPLE 4 Material.Noble combing wool of 23 microns average fibrediameter. 1 tex. nylon filament.

Method.The twisting was accomplished with the arrangement shown inFIGURE 6 with one 53 tex. wool strand being self-twisted with one 1 tex.nylon filament and the resultant thread being self-twisted at the secondstage with a second 1 tex. nylon filament.

The roller units each had a 3 inch stroke and 22 cms. cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strands due to the first set of rollers.

Yarn properties.The yarn count was 55 tex. and its tenacity was 6.0gm./tex. with a coeflicient of variation of strength of 13%.

The mean extension to break was 12% and the yarn was 96% wool and 3 /2nylon.

This yarn was suitable for use as a warp yarn in weavmg.

EXAMPLE 5 Material.-Noble combing wool of 23 microns average fibrediameter. 2 tex. multi-filament (7 fil.) nylon yarn.

Method.The twisting was accomplished with the arrangement shown inFIGURE 7. Two 26.5 tex. all wool strands were twisted in the first pairof twisting rollers and r converged to form an intermediate yarn. Thisyarn and the 2 tex. multi-filament (7 fil.) were passed through thesecond set of twisting rollers and were converged to form the resultantyarn.

The roller units each had a 3-inch stroke and 22 cms. cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strands due to the first set of rollers.

Yarn properties.The yarn count was 55 tex. and the tenacity was 5.6gm./tex. with a coefiicient of variation of strength of 15%.

The mean extension to break was 15% and the yarn was 96 /2% wool and 3/2% nylon.

This yarn was suitable for use as a warp yarn in weavmg.

. EXAMPLE 6 Material.Noble combing wool of 23 microns average fibrediameter. 2 tex. multi-filament (7 fil.) nylon yarn.

Method.The twisting was carried out with the arrangement of FIGURE 7.One 51 tex. wool strand was self-twisted with one 2 tex. multi-filament(7 fil.) nylon yarn by the first set of twisting rollers to form theintermediate yarn and this intermediate yarn was then selftwisted at thesecond stage with a second 2 tex. multi-filament (7 fil.) nylon yarn.

The roller units each had a 3-inch stroke and 22 cms. cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strands due to the first set of rollers.

Yarn properties.The yarn count was 55 tex. and the tenacity was 6.5gm./tex. with a coefiicient of variation of strength of 7.0%.

The mean extension to break was 16% and the yarn was 92 /2% wool and 7/2% nylon.

This yarn was suitable for use as a warp yarn in weavmg.

EXAMPLE 7 Material.Noble combing wool of 23 microns average fibrediameter. 1 tex. nylon strand.

Method.The twisting was accomplished with the arrangement of FIGURE 7,two wool strands being selftwisted together at the first stage to forman intermediate yarn of 29 tex. and this yarn was self-twisted with onetex. nylon strand in the second stage to form the resultant yarn.

The roller units each had a 3-inch stroke and 22 cms. cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strands due to the first set of rollers.

Yarn properties.The yarn count was 30 tex. and the tenacity was 5.0gm./tex. with a coefiicient of variation of strength of 18%.

The mean extension to break was 13% and the yarn was 96 /2% wool and3'/2% nylon.

This 30 tex. yarn of 96 /2t% wool was suitable for use as a warp yarn inweaving.

EXAMPLE 8 Material.Noble combing wool of 23 microns average fibrediameter. 1 tex. nylon filament.

Method.The twisting was accomplished with the arrangement of FIGURE 7.One 28 tex. wool strand was self-twisted with one 1 tex. nylon filamentat the first stage to produce an intermediate yarn and the intermediateyarn was self-twisted with one 1 tex. nylon filament at the secondstage.

The roller units each had a 3-inch stroke and 22 cms. cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strand due to the first set of rollers.

Yarn properties.The yarn count was 30 tex. and the tenacity was 6.3gm./tex. with a coefiicient of variation of strength of 12%.

The mean extension to break was 14% and the yarn was 93% wool and 7%nylon.

This 30 tex. yarn of 93% wool was suitable for use as a warp yarn inweaving.

EXAMPLE 9 Material.--Noble combing wool of 26 microns average fibrediameter.

Method.The twisting was achieved with the arrangement shown in FIGURE 3.Four wool strands were passed through the first pair of twisting rollersand converged to form two intermediate yarns which were then passedthrough the second set of rollers and then self-twisted to- 9 gether toform a resultant all wool yarn having the structure of FIGURE 5.

The roller units each had a 3-inch stroke, and 22 cms cycle length andwere phased relative to each other so that in the final yarn theresultant yarn twist due to the second set of rollers had change-overpoints exactly midway between the twist change-over points in theindividual strands due to the first set of rollers.

The number of turns of plied twist in each half cycle of plied twist inthe intermediate yarns was 38 and the number of turns of plied twist perhalf cycle of plied twist in the final yarn due to the second set oftwisting rollers was 20.

Yarn properties. -The yarn count was 90 tex. and the tenacity was 6.3gm./tex. with a coefiicient of variation of strength of 9%.

The mean extension to break was 20% This 90 Tex wool yarn was suitablefor weaving but not for knitting because of loop distortion.

EXAMPLE 10 Material.Noble combing wool of 26 microns average fibrediameter.

Method-Twisting was accomplished with the arrangement of FIGURE 6. Thestroke of the first pair of twisting rollers was 2", and the stroke ofthe second pair of twisting rollers was 1 inch. The path length of oneintermediate yarn between the two pairs of rollers was lengthened sothat the twist change-over points of one intermediate yarn fell exactlymidway between the twist change-over points of the other intermediateyarn. Phasing between the two pairs of rollers was adjusted so that inthe final yarn the resultant yarn twist due to the second set of rollerseach of its changeover points exactly midway between a twist change-overpoint in one intermediate yarn and a twist change-over point in theother intermediate yarn.

Yarn properties-The yarn count was 90 tex. and the tenacity was 3.4gm./tex. with a coefiicient of variation of strength of 13%.

The mean extension to break was 9% The number of turns of plied twistper half cycle of plied twist in the intermediate yarns due to the firstpair of twist rollers was 28 and the number of turns of plied twist perhalf cycle of plied twist in the final yarn due to the second pair oftwist rollers was 8.

It will be seen that the twist levels at both stages in the preparationof this yarn were very much reduced compared with the twist levels inthe yarn in Example 9. It was found that this 90 tex. wool yarn wassuitable for knitting.

Special properties can be induced into yarns by manipulation of thevarious parameters efiecting the yarn and the basic characteristics ofthe raw material. We have already shown that when producing afour-strand knitting yarn it is preferred that one of the intermediateyarns should traverse a longer path length than the other intermediateyarn as they pass to the second set of twisting rollers whereas whenproducing a warp yarn for weaving it is preferred that both path lengthsshould be the same. It is of course also possible to alter the pathlength of one of the yarns travelling from the second set of twistingrollers to the final convergence guide in order to phase the zones ofsuperimposed twist in the two yarns with respect to one another. It mayalso be desired to phase the twist distributions in individual strandsleaving the first set of twisting rollers with respect to one anotherbefore they are converged to form an intermediate yarn. Furthermore, thetwist levels can be varied by altering parameters other than the strokesof the twisting rollers. The twist levels could, for example,

be varied considerably if strands of different material are used.

I claim:

1. A process for forming a stable twisted thread assembly, comprisingthe steps of individually twisting at least one strand of a group ofstrands so that each twisted strand has repeated along its lengthsuccessive zones of opposite twist separated by strand twist changeoverregions at which there is no twist, converging the strands of the groupso that they twist around one another such as to form a stable firstthread having successive zones of opposite plying twist separated byplying twist change-over regions at which there is no plying twist,twisting said first thread to superimpose alternately opposite twist insuccessive zones along its length which latter zones are separated bysuperimposed twist changeover regions of no superimposed twist, andconverging the twisted first thread with a second thread so that the twothreads twist around one another to form a stable twisted assembly.

2. A process as claimed in claim 1, in which the second thread, beforeit is converged with the first thread, is twisted such as to impartalternately opposite twist to successive zones along its length whichlatter zones are separated by change-over regions of no imparted twist.

3. A process as claimed in claim 2, in which the threads are convergedwith zones of like superimposed and imparted twist in phase and withtheir change-over regions of no superimposed and no imparted twistcoincident.

4. A process as claimed in claim 1, in which at least two strands ofsaid group are individually twisted before the strands of the group areconverged so that each twisted strand of the group has repeated alongits length successive zones of opposite twist separated by strand twistchange-over regions at which there is no twist.

5. A process as claimed in claim 4, in which the twisted strands of thegroup are converged with like twist zones in phase and with their strandtwist changeover regions coincident when forming the first thread.

6. A process as claimed in claim 1, in which said second thread isformed by individually twisting at least one of the strands of thefurther group of strands so that each twisted strand of said furthergroup has repeated along its length successive zones of opposite twistseparated by strand twist change-over regions at which there is no twistand converging the strands of the further group so that they twistaround one another such as to form said second thread as a stableassembly having successive zones of opposite plying twist separated byplying twist change-over regions at which there is no plying twist.

7. A process as claimed in claim 6, in which at least two strands ofsaid further group are individually twisted so that each has repeatedalong its length successive zones of opposite twist separated by strandtwist change-over regions at which there is no twist before the strandsof said further group are converged.

8. A process as claimed in claim 7, in which the twisted strands of saidfurther group are converged with like twist zones in phase and withtheir strand twist change-over regions coincident when forming thesecond thread.

9. A process as claimed in claim 6, in which the first and secondthreads are converged with the zones of strand twist in the first threadin phase with zones of like strand twist in the second thread.

10. A process as claimed in claim 6, in which the first and secondthreads are converged with the zones of strand twist in the first threadout of phase with the zones of like strand twist'in the second thread.

11. Apparatus for producing a stable twisted thread assembly, comprisingfirst twisting means to impart alternating zones of opposite strandtwist to each strand of a group of strands, first converging meansadjacent the first twisting means to converge the first group of strandsto form a first thread, second twisting means to superimpose alternatingzones of opposite twist upon the first thread and second convergingmeans adjacent the second twisting means to converge the first threadwith a second thread.

12. Apparatus for producing a stable twisted thread assembly, comprisinga first pair of oppositely rotated transversely reciprocating twistingrollers simultaneously to impart alternating zones of opposite strandtwist to each strand of a first and second group of strands, firstconverging means adjacent the first pair of twisting rollers to convergethe first group of strands to form a first thread and also to convergethe second group of strands to form a second thread, a second pair ofoppositely rotated transversely reciprocating rollers simultaneously tosuperimpose alternating zones of opposite twist individually upon thefirst and second threads, and

second converging means adjacent said second pair of twisting rollers toconverge the first and second threads.

References Cited UNITED STATES PATENTS STANLEY N. GILREATH, PrimaryExaminer.

WERNER H. SCHROEDER, Assistant Examiner.

U.S. C1. X.R. 57--59, 77.3, 156

